Animal Reproduction
& Development
(Ch. 46, 47)
A “homunculus” inside the head of a
human sperm
Sexual & asexual reproduction
• Asexual
– offspring all have same genes (clones)
– no variation
• Sexual
– gametes (sperm & egg)  fertilization
– mixing of genes  variation
2005-2006
Parthenogenesis
• Development of an unfertilized egg
– honey bees
• drones = males produced through parthenogenesis 
haploid
• workers & queens = females produced from fertilized
eggs  diploid
queen
2005-2006
worker
drone
•
•
•
Honey bee eggs hatch regardless of whether the are fertilized. The female bees--queens &
workers--develop from fertilized eggs that contain 32 chromosomes. These 32 chromosomes
consist of two sets of 16, one set from each parent. Hence female bees are said to be diploid
in origin. The males (drones) develop from unfertilized egg which contain only one set of 16
chromosomes from their mother. Drones are thus haploid in origin This reproduction by the
development of unfertilized eggs is called parthenogenesis
Drones develop by parthenogenesis from unfertilized eggs that the queen produces by
withholding sperm from the eggs laid in large drone cells. Drones lack stings and the
structures needed for pollen collection; in the autumn they are ejected by the colony to
starve, unless the colony is queenless. New drones are produced in the spring for mating.
Both queens and workers are produced from fertilized eggs. Queen larvae are reared in
special peanut-shaped cells and fed more of the pharyngeal gland secretions of the nurse
bees (bee milk or royal jelly) than the worker larvae are. The precise mechanism for this caste
differentiation is still uncertain. Although workers are similar in appearance and behavior to
other female bees, they lack the structures for mating. When no queen is present to inhibit
the development of their ovaries, however, workers eventually begin to lay eggs that develop
into drones.
Different strokes…
gay
penguins
parthenogenesis in aphids
“lesbian” lizards
2005-2006
sex-change in fish
Hermaphrodites
• Having functional
reproductive system of
both sexes
earthworms mating
flat worm
Fertilization
• Joining of egg & sperm
– external
• usually aquatic animals
– internal
• usually land animals
2005-2006
Development
• External
– development in eggs
– fish & amphibians in water
• soft eggs= exchange across membrane
– birds & reptiles on land
• hard-shell amniotic eggs
• structures for exchange of food, O2 & waste
– sharks & some snakes
• live births from eggs
• Internal
– placenta
• exchange food & waste
– live birth
Adaptive advantages?
• What is the adaptive value of each type
of sexual reproduction
– number of eggs?
– level of parental of care
– habitat?
2005-2006
Reproductive hormones
• Testosterone
– from testes
– functions
• sperm production
• 2° sexual
characteristics
LH &
FSH
• Estrogen
– from ovaries
– functions
• egg production
• prepare uterus for
fertilized egg
• 2° sexual
characteristics
testes
or
ovaries
2005-2006
Male reproductive
system
• Sperm production
– over 100 million produced per day!
2005-2006
– ~2.5 million released
per drop!
Spermatogenesis
Epididymis
Testis
Coiled
seminiferous
tubules
Germ cell
(diploid)
1°
spermatocyte
(diploid)
MEIOSIS I
2°
spermatocytes
(haploid)
MEIOSIS II
Vas deferens
Spermatids
(haploid)
Spermatozoa
Cross-section of
seminiferous tubule
Female reproductive system
Female reproductive system
2005-2006
Menstrual cycle
LH
FSH
Hypothalamus
GnRH
egg development
ovulation = egg release
corpus luteum
Pituitary
FSH & LH
estrogen
progesterone
Ovaries
lining of uterus
estrogen
Body cells
2005-2006
days 0
7
14
21
28
Egg maturation in ovary
• Corpus luteum
– produces
progesterone
to maintain
uterine lining
2005-2006
Female hormones
• FSH & LH
– release from pituitary
– stimulates egg development & hormone release
– peak release = release of egg (ovulation)
• Estrogen
– released from ovary cells around developing egg
– stimulates growth of lining of uterus
– lowered levels = menstruation
• Progesterone
– released from “corpus luteum” in ovaries
• cells that used to take care of developing egg
– stimulates blood supply to lining of uterus
– lowered levels = menstruation
Oogenesis
What is the
advantage of
this development
system?
• Unequal meiotic divisions
– unequal distribution
of cytoplasm
– 1 egg
– 2 polar bodies
Meiosis 1 completed
during egg maturation
ovulation
Meiosis 2 completed
triggered by fertilization
Put all your egg
in one basket!
Fertilization
•
•
•
•
•
fertilization
cleavage
gastrulation
neurulation
organogenesis
Fertilization
• Joining of sperm & egg
– sperm head (nucleus) enters egg
What is the effect of sperm binding on
Ca2+ distribution in the egg?
EXPERIMENT
A fluorescent dye that glows when it binds free Ca2+ was injected into unfertilized sea urchin eggs. After sea urchin
sperm were added, researchers observed the eggs in a fluorescence microscope.
500 m
RESULTS
1 sec before
fertilization
10 sec after
fertilization
Point of
Sperm
entry
20 sec
30 sec
Spreading wave
of calcium ions
CONCLUSION The release of Ca2+ from the endoplasmic reticulum into the cytosol at the site of sperm entry triggers the release
of more and more Ca2+ in a wave that spreads to the other side of the cell. The entire process takes about 30 seconds.
Timeline for the fertilization of sea urchin eggs
1
Binding of sperm to egg
2
Acrosomal reaction: plasma membrane
depolarization (fast block to polyspermy)
3
4
6
8
10
Increased intracellular calcium level
20
Cortical reaction begins (slow block to polyspermy)
30
40
50
1
Formation of fertilization envelope complete
2
Increased intracellular pH
3
4
5
Increased protein synthesis
10
20
Fusion of egg and sperm nuclei complete
30
40
Onset of DNA synthesis
60
90
First cell division
Cleavage
• Repeated mitotic divisions of zygote
– 1st step to becoming multicellular
– unequal divisions establishes body plan
• different cells receive different portions of egg
cytoplasm & therefore different regulatory
signals
Cleavage
• zygote  morula  blastula
– establishes future development
zygote
gastrulation
morula
blastula
Gastrulation
• Establish 3 cell layers
gastrulation in
primitive chordates
– ectoderm
• outer body tissues
– skin, nails, teeth,nerves, eyes,
lining of mouth
– mesoderm
• middle tissues
– blood & lymph, bone &
notochord, muscle, excretory &
reproductive systems
– endoderm
• inner lining
– digestive system, lining of
respiratory, excretory &
reproductive systems
protostome vs. deuterostome
ectoderm
mesoderm
endoderm
Testing…
All of the following correctly describe the fate of the embryonic
layers of a vertebrate EXCEPT
A. neural tube and epidermis develop from ectoderm
B. linings of digestive organs and lungs develop from
endoderm
C. notochord and kidneys develop from endoderm
D. skeletal muscles and heart develop from mesoderm
E. reproductive organs and blood vessels develop from
mesoderm
Testing…
In a study of the development of frogs, groups of cells in the
germ layers of several embryos in the early gastrula stage were
stained with five different dyes that do not harm living tissue.
After organogenesis (organ formation), the location of the dyes
was noted, as shown in the table below.
Tissue
Brain
Notochord
Liver
Lens of the eye
Lining of the digestive tract
Stain
Red
Yellow
Green
Blue
Purple
Neurulation
• Formation of notochord & neural tube
– develop into nervous system
Neural tube
Notochord
develops into
vertebral column
develops into CNS
(brain & spinal cord)
Organogenesis
Mammalian embryo
Umbilical blood vessels
Chorion
Bird embryo
Amnion
Yolk
sac
Allantois
Fetal blood vessels
Placenta
Maternal blood vessels
Four stages in early embryonic development of
a human
Endometrium
(uterine lining)
Inner cell mass
Trophoblast
1
Blastocoel
Blastocyst
reaches uterus.
Maternal
blood
vessel
Expanding
region of
trophoblast
Epiblast
Hypoblast
Trophoblast
2 Blastocyst
implants.
Expanding
region of
trophoblast
Amnion
Amniotic
cavity
Epiblast
Hypoblast
3
Extraembryonic
membranes
start to form and
gastrulation begins.
Chorion (from
trophoblast)
Extraembryonic mesoderm cells
(from epiblast)
Allantois
Yolk sac (from
hypoblast)
Amnion
Chorion
Ectoderm
Mesoderm
Endoderm
4 Gastrulation has produced a threelayered embryo with four
extraembryonic membranes.
Yolk sac
Extraembryonic
mesoderm
Sources of developmental
information for the early embryo
Unfertilized egg cell
Sperm
Molecules of a
a cytoplasmic
determinant
Molecules of
another cytoplasmic deterNucleus
minant
Fertilization
Zygote
(fertilized egg)
Mitotic cell division
Two-celled
embryo
(a) Cytoplasmic determinants in the egg. The unfertilized egg cell has molecules in its cytoplasm,
encoded by the mother’s genes, that influence development. Many of these cytoplasmic
determinants, like the two shown here, are unevenly distributed in the egg. After fertilization
and mitotic division, the cell nuclei of the embryo are exposed to different sets of cytoplasmic
determinants and, as a result, express different genes.
Early embryo
(32 cells)
NUCLEUS
Signal
transduction
pathway
Signal
receptor
Signal
molecule
(inducer)
(b)
Induction by nearby cells. The cells at the bottom of the early embryo depicted here are releasing
chemicals that signal nearby cells to change their gene expression.
Cell signaling and induction during development
of the nematode
Epidermis
2
Anterior
1
3
Posterior
4
Signal
Gonad Anchor cell protein
Receptor Signal
protein
EMBRYO
4
3
Vulval precursor cells
Signal
Anterior
daughter
cell of 3
Posterior
daughter
cell of 3
Will go on to
form muscle
and gonads
ADULT
Inner vulva Outer vulva
Will go on to
form adult
intestine
Epidermis
(a) Induction of the intestinal precursor cell at the
four-cell stage.
(b) Induction of vulval cell types during larval
development.
The effect of the bicoid gene, a maternal effect (eggpolarity) gene in Drosophila
Tail
Head
T1
T2
T3
A1 A2 A3 A4 A5
A6 A7
A8
Wild-type larva
Tail
Tail
A8
A7
Mutant larva (bicoid)
A8
A6
A7
(a) Drosophila larvae with wild-type and bicoid mutant phenotypes. A mutation
in the mother’s bicoid gene leads to tail structures at both ends (bottom larva).
The numbers refer to the thoracic and abdominal segments that are present.
Nurse cells
Egg cell
1 Developing
egg cell
bicoid mRNA
2 Bicoid mRNA
in mature
unfertilized egg
Fertilization
Translation of bicoid mRNA
100 µm
3 Bicoid protein in
early embryo
Anterior end
(b) Gradients of bicoid mRNA and bicoid protein in normal egg and early embryo.
Conservation of homeotic genes in a
fruit fly and a mouse
Adult
fruit fly
Fruit fly embryo
(10 hours)
Fly
chromosome
Mouse
chromosomes
Mouse embryo
(12 days)
Adult mouse
Effect of differences in Hox gene expression during
development in crustaceans and insects
Thorax
Thorax
Genital
segments
Abdomen
Abdomen
Mutant Drosophila with an extra
small eye on its antenna
Vertebrate limb development
(a) Organizer regions. Vertebrate limbs develop from
protrusions called limb buds, each consisting of
mesoderm cells covered by a layer of ectoderm.
Two regions, termed the apical ectodermal ridge
(AER, shown in this SEM) and the zone of polarizing
activity (ZPA), play key organizer roles in limb
pattern formation.
Anterior
AER
ZPA
Posterior
Limb bud
Apical
ectodermal
ridge
50 µm
(b) Wing of chick embryo. As the bud develops into a
limb, a specific pattern of tissues emerges. In the
chick wing, for example, the three digits are always
present in the arrangement shown here. Pattern
formation requires each embryonic cell to receive
some kind of positional information indicating
location along the three axes of the limb. The AER
and ZPA secrete molecules that help provide this
information.
Digits
Anterior
Ventral
Distal
Proximal
Dorsal
Posterior
What role does the zone of polarizing activity (ZPA) play
in limb pattern formation in vertebrates?
EXPERIMENT
ZPA tissue from a donor chick embryo was transplanted under the ectoderm in the
anterior margin of a recipient chick limb bud.
Anterior
Donor
limb
bud
New ZPA
Host
limb
bud
ZPA
Posterior
RESULTS
In the grafted host limb bud, extra digits developed from host tissue in a mirror-image
arrangement to the normal digits, which also formed (see Figure 47.26b for a diagram of a normal
chick wing).
CONCLUSION The mirror-image duplication observed in this experiment suggests that ZPA cells secrete
a signal that diffuses from its source and conveys positional information indicating “posterior.” As the
distance from the ZPA increases, the signal concentration decreases and hence more anterior digits develop.
Sex determination
Sperm
Ovum
Y
Zygote
XY
X
SRY
Indifferent
gonads
No SRY
X
Ovum
X
Sperm
Develop in
early
embryo
Testes
XX
Zygote 2005-2006
Seminiferous
tubules
Leydig cells
Ovaries
(Follicles do not
develop until
third trimester)
Placenta
• Materials exchange
across membranes
Placental circulation
Maternal
arteries
Maternal
veins
Placenta
Maternal portion
of placenta
Umbilical cord
Chorionic villus
containing fetal
capillaries
Fetal portion of
placenta (chorion)
Maternal blood
pools
Uterus
Fetal arteriole
Fetal venule
Umbilical cord
Umbilical arteries
Umbilical vein
Human fetal development
4 weeks
7 weeks
Human fetal development
10 weeks
Human fetal development
12 weeks
20 weeks
Human fetal development
• The fetus just spends much of the 2nd & 3rd
trimesters just growing
…and doing various flip-turns & kicks inside
amniotic fluid
Week 20
Human fetal development
• 24 weeks (6 months; 2nd trimester)
fetus is covered
with fine, downy
hair called
lanugo. Its skin is
protected by a
waxy material
called vernix
Human fetal development
• 30 weeks (7.5 months)
umbilical cord
Getting crowded in there!!
• 32 weeks (8 months)
The fetus sleeps
90-95% of the
day &
sometimes
experiences
REM sleep, an
indication of
dreaming
positive feedback
from
ovaries
Birth
Oxytocin
from fetus
and mother's
posterior pituitary
Induces oxytocin
receptors on uterus
Stimulates uterus
to contract
Stimulates
placenta to make
Prostaglandins
Stimulate more
contractions
of uterus
Positive feedback
Estrogen
The end of the journey!
And you think
9 months of
AP Bio is hard!
Mechanisms of some contraceptive methods
Female
Male
Method
Event
Event
Method
Production of Production of
viable sperm viable oocytes
Vasectomy
Sperm transport Ovulation
down male
duct system
Abstinence
Combination
birth control
pill (or injection,
patch, or
vaginal ring)
Abstinence
Condom
Coitus
interruptus
(very high
failure rate)
Sperm Capture of the
deposited oocyte by the
in vagina
oviduct
Tubal ligation
Sperm
Transport
movement of oocyte in
through
oviduct
female
reproductive
tract
Spermicides;
diaphragm;
cervical cap;
progestin alone
(minipill, implant,
or injection)
Meeting of sperm and oocyte
in oviduct
Union of sperm and egg
Morning-after
pill (MAP)
Progestin alone
Implantation of blastocyst
in properly prepared
endometrium
Birth
Reproductive Cloning of a Mammal by
Nuclear Transplantation
APPLICATION This method is used to produce cloned
animals whose nuclear genes are identical to the donor
animal supplying the nucleus.
1
RESULTS
The cloned animal is identical in appearance
and genetic makeup to the donor animal supplying the nucleus,
but differs from the egg cell donor and surrogate mother.
2
Egg cell
from ovary Nucleus
Nucleus
removed
3 Cells fused
removed
TECHNIQUE
Shown here is the procedure used to produce
Dolly, the first reported case of a mammal cloned using the nucleus
of a differentiated cell.
Egg cell
donor
Mammary
cell donor
Cultured
mammary cells
are semistarved,
arresting the cell
cycle and causing
dedifferentiation
Nucleus from
mammary cell
4 Grown in culture
Early embryo
5 Implanted in uterus
of a third sheep
6 Embryonic
development
Surrogate
mother
Lamb (“Dolly”)
genetically identical to
mammary cell donor
Copy Cat, the first cloned cat
Working with stem cells
Embryonic stem cells
Adult stem cells
Early human embryo
at blastocyst stage
(mammalian equivalent of blastula)
From bone marrow
in this example
Totipotent
cells
Pluripotent
cells
Cultured
stem cells
Different
culture
conditions
Different
types of
differentiated
cells
Liver cells
Nerve cells
Blood cells
Any Questions?
Make sure you can do the following:
1. Label all parts of the male and female reproductive
systems and explain how they contribute to the
functions of the systems.
2. Explain the major phases of animal development.
3. Demonstrate how reproductive technologies might
have moral and ethical implications for society
4. Explain the causes of reproductive system disruptions
and how disruptions of the reproductive system can
lead to disruptions of homeostasis.